Mail cannot save information about your mailboxes because there isn't enough space in your home folder

Long support conversation with Apple today, first level person, just involved full power down / unplug restart, and then repairing permissions. No effect. I had to stop at that point, but they were suggesting reinstalling Catalina next. Has anyone tried that?

I installed the supplemental update and so far I haven't had the error. Like 8 hours so far. Also, search in mail is working now where it was pretty broken before. Will let you know if the error returns ...

I have spent few hours with Apple support. They have no idea how to fix this issue. And like a bonus, my iCloud is not syncing, Adobe Illustrator keeps crushing from time to time....so I am loosing my mind :D I've had so many issues in past year. Keyboard replacement on two new MacBooks etc..

Apple Support reached out proactively, apparently based on engineering wanting to get to the bottom of this issue. I was able to capture a sysdiagnose a few minutes after one of these errors occurred and it is now in the hands of engineering.

Same problem, and unfortunately cllivesey's solution didn't work for me. I have 388 GB free space on my hard drive and 129 GB free on iCloud Drive. I'm also experiencing very high CPU usage by Mail when it is running. Along with the serious downgrades with the loss of iTunes I am definitely regretting the move to Catalina.

Hi All,

Unfortunately my solution only worked for a brief period of time and the issue re-occurred, apologies :-(.

This looks to still be a massive issue, I’ve had to roll back to Mojave. I’ve had not issues with Catalina on my MacBook Pro (except the annoying security confirmations on every app I use), only on my Mac Mini.

Hope this is resolved ASAP.

Same here. The problem had gone away for a while but reappeared this morning. Computer slowed to a crawl, disk scraping away in the background, beachball spinning, got the application out of memory warning and the Mail message reporting out of disk space.

sounds familiar!!

The apple support team have now referred my case to the Engineering department for resolution. The feedback I had today is that they have seen a small number of cases with similar symptoms so are likely to develop and release a fix in one of the software updates in the near future

I tried the fix posted by clivesey 10th Oct 2019 1:03AM but still have the same problem. I have also tried clearing out all my mails in all my accounts (iCloud mail; gmail, hotmail) and applying the fix again. Still same problem. I have lots of space on my mac ( 64GB available of a 600GB SSD/flash 'fusion' drive) and am using iCloud storage where I also have tons of available space (1,8TB available!). Hope there comes a Catalina fix soon addressing this problem.

We can try to help Apple to help us, listing the characteristics of the computers that have problems. Mine is late 2015 iMac, with fusion drive 1TBssd+24GBssd (400GB free), Intel Iris Pro Graphics 6200, 8+8GB RAM, monitor retina. With macOS 10.15.1 I've problem with Mail (there isn't enough space in your home folder...) and also downloading with Chrome (disk full).

iMac 5K 2017 with Fusion Drive (750 GB SSD + 4 TB HDD) having 200 GB free space, 32 GB RAM.

Fusion Drive was previously used on an iMac 2011, was HFS+ before being converted to APFS with the Mojave install one year ago.

I have the feeling this is a Fusion Drive / APFS related issue.

I noticed that my first fusion SSD is SATA (1TB) and the other one is NVMExpress (24GB). My colleague with iMac 2013 and fusion drive has two SATA SSD disks instead and has no problems with Catalina. Helpful?

Hi all,

After I first posted, things went from bad to worse. Mail disk space errors, out of memory errors, iCloud calendar lost all its data, unfixable fusion drive errors..., loss of recovery partition, unable to safe boot....

Had to erase, repartition, reinstall Catalina 10.15.1 from USB, reinstall from a carbon copy cloner backup.

2 weeks of inconvenience, 48 hours of downtime, not impressed by this OS iteration.

Here are my specs below. Also a fusion drive.

 Model Name: iMac

  Model Identifier: iMac17,1

  Processor Name: Quad-Core Intel Core i7

  Processor Speed: 4 GHz

  Number of Processors: 1

  Total Number of Cores: 4

  L2 Cache (per Core): 256 KB

  L3 Cache: 8 MB

  Hyper-Threading Technology: Enabled

  Memory: 16 GB

  Boot ROM Version: 173.0.0.0.0

  SMC Version (system): 2.34f3

So far then, it appears that everyone with the problem is running a Fusion drive. And that the problem is not limited to Mail app only.

So to state the Captain Obvious conclusion, it appears this is not mail, but Catalina not correctly supporting / corrupting Fusion drives. Probably some subset of Fusion drives because it appears to be working for some on Fusion drives.

My specific case is that my iMac had a factory SSD + HD setup, then the HD failed and was replaced by a SATA SSD, but that was set up as a Fusion drive with the original SSD.

Sorry the formatting of my reply is so bad. (Copy / Paste from Notes doesn't work apparently).

Here is a better formatted reply:

The issue is still not solved from my experience.

I essentially followed those steps but my iMac still has the problem! Details below: 

Perhaps the issue also is related to how the fusion drive partitions are formatted. 

I formatted the two partitions as APFS encrypted. 

My experience was:

Booted from the Catalina OS stick and erased the "Macintosh HD" volume from the Disk Utility that was available on the install medium.  

First erase failed and resulted in two partitions 

disk0s2 121,12GB

disk1s2 479,89GB

Then I performed the following using the disk utility

disk0s2 erased and created a new volume Mac120GB   APFS encrypted  (with my chosen encryption pw)

disk1s2 erased and created a new volume MacOS480GB  APFS encrypted (with the same chosen encryption pw)

I did clean installation of MacOS Catalina to MacOS480GB.

Problem was that now my 'Fusion' drive was now split. It consisted of an SSD (with MacOS installed) and a Flash drive i.e. two separate drives. 

At this point I discovered the “diskutil resetfusion” possibility… 

So I followed the steps suggested i.e.

- Create bootable USB with macOS 10.15.1 (or latest)  (…already done in my first attempt

- Restart Mac and press with Cmd + Option + R to start recovery mode

- In recovery mode open Terminal and enter "diskutil resetfusion"

- Install macOS

Then used the migration assistant to restore my software and data from my Time Machine backup.

>> the migration assistant is in the utilities folder of the applicaton folder

>> choose migration from a time machine backup

And now I have the issue!